Embodiments of the present invention generally relate to radiation sensitive photoresist materials and methods of manufacturing and patterning such photoresists.
In the manufacture of integrated circuits (IC) or chips, patterned exposure of light is used to define useful shapes or features on the surface of a substrate such a semiconductor wafer, typically in a photosensitive photoresist material. Feature sizes on chips are continually becoming smaller, requiring more sophisticated shorter wavelength lithography technologies. Next generation lithography (NGL) is expected to replace the current optical lithography method, for example, in the 20 nm technology node and beyond. Extreme ultraviolet (EUV) lithography (EUVL) EUVL shows promise as a next generation lithography technique, as well as electron beam (e-beam) lithography.
Extreme ultraviolet lithography (“EUVL”) employs short wavelength radiation (“light”) in the approximate range of 10 nanometers (nm) to 15 nm to pattern features having a size smaller than 100 nm. Because extreme ultraviolet (“EUV”) radiation is absorbed in almost all materials, a mask used in the EUVL is a reflective mask. The reflective mask reflects the radiation in certain regions and absorbs the radiation in other regions of the mask. Light reflected from the mask reproduces an image of the mask on photoresist (or “resist”) disposed on a wafer substrate such as silicon. When illuminated or exposed to radiation, the photoresist undergoes chemical reactions and is then developed to produce a replicated pattern of the mask on the wafer.
However, as pattern sizes shrink, thicker photoresists are problematic. Such problems arise during development, where the surface tension the solution pulls on the lines of the pattern, which is known as pattern collapse. Thus, there is a need for thinner photoresists, to achieve lower aspect ratios of the features, as well as preventing pattern collapse.
Desirable attributes of resist materials sensitive to radiation include one or more of robust adhesion, thermal and mechanical stability, and removability using plasma etching or stripping, for example, oxygen plasma etching. Since EUV and other types of lithography exposures, such as e-beam, are conducted under vacuum, outgassing of volatile components, which may contaminate expensive reflective multilayer optical elements, should be minimized or eliminated. It may also be desirable for the resist to exhibit sufficient conductivity to minimize proximity effects associated with secondary electrons generated during exposure to radiation.